The invention relates to a device for circular and/or profile grinding having a receiving device for a workpiece and having a tool, which can be driven to perform rotations and has an abrasive coating.
In devices of this type, grinding tools are used in the form of disks which, on their outer circumference, are provided with an abrasive coating. By means of devices of this type, it is possible to grind workpieces to a circular shape and/or to grind profiles, for example, in the form of recesses with radial or conical shoulders. If in this case left and right shoulders are to be ground at a workpiece, it is as a rule necessary to rechuck the workpiece. However, this rechucking often carries the risk of inaccuracies.
An object of the invention is to construct a device of the initially mentioned type such that the grinding process can be rationalized.
This object is achieved in that the grinding tool is constructed in the shape of a ring which is provided with the abrasive coating on its interior circumference.
The use of this type of a grinding tool results in several surprising advantages. On the one hand, it is possible to shape opposite shoulders of a workpiece--so-called right and left shoulders--with the same chucking, particularly if the axis of rotation of the grinding tool is sloped with respect to the axis of rotation of the workpiece. The grinding tool can reach both shoulders, in that only the corresponding feeds are operated and without any rechucking of the workpiece. Another, very important advantage is that, by means of the new grinding tool, significantly higher grinding speeds can be achieved and thus significantly shorter processing times. In the case of the conventional grinding tools, the grinding speed, i.e., the circumferential speed of the abrasive coating, is limited mainly by the occurring centrifugal forces which, if certain rotational speed limits are exceeded, lead to a destruction of the abrasive coating. In the case of the new grinding tool, on the other hand, the abrasive coating is supported with respect to the centrifugal forces by means of the interior circumference of the ring so that the centrifugal forces affecting the abrasive coating practically no longer limit the grinding speed. Care must only be taken that the ring-shaped grinding tool itself and its holding elements withstand the centrifugal forces occurring at high rotational speeds.
In a further development of the invention, it is provided that the ring-shaped grinding tool is held in a ring-shaped holder which is pivoted and is connected with a rotating drive.
In order to permit, in a further development of the invention, a construction that is as compact as possible, it is provided that the ring-shaped holder is constructed as the rotor of an electric motor. As a result, a space-saving arrangement can be achieved.
In a further development of the invention, it is provided that the ring-shaped holder is supported by means of a gas bearing. This type of a gas bearing permits very high rotational speeds, without the occurrence of any significant wear.
The holder for the grinding tool, which rotates along with it, is subjected to the same high centrifugal forces so that it must be designed correspondingly for very high rotational speeds. In order to permit maximum rotational speeds, in the case of relatively large diameters of the ring-shaped grinding tool, it is provided in a further development that the ring-shaped holder is constructed as a composite body which has a basic body made of metal receiving the grinding tool and a reinforcement surrounding this basic body. The basic body, which consists of metal, has essentially the objective of ensuring dimensional stability, while the reinforcement surrounding it has the purpose of absorbing the forces which occur at extremely high rotational speeds of 10,000 min.sup.-1 or more. In this case, it is provided in a particularly advantageous development of the invention that the reinforcement is formed by fibers extending in circumferential direction which are embedded in a matrix made of plastic. For this purpose, carbon fibers are suitable or filaments known by the trade name "Keflar" which are saturated with plastic and are wound around the basic body. In this case, it is provided that the fibers of these reinforcements are aligned unidirectionally in circumferential direction so that particularly high strengths are obtained in circumferential direction.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.